Cathode-ray tube, more particularly for colour television



Feb. 12, 1957 BRI-:E ETAL 2,781,469

P. VAN

CATHODE-RAY TUBE, MORE PARTICULARLY FOR COLOUR TELEVISION Filed Oct. 20,1953 ,y MW 400001 l lllll INVENTORS PIETER VAN BREE THEODORUSHAGENBEFIGY AGENT CATHODE-RAY TUBE, MORE PARTICULARLY FOR COLOURTELEVISION Pieter van Bree and Theodorus Hagenberg, Eindhoven,Netherlands, assgnors to Hartford National Bank and Trust Company,Hartford, Conn., as trustee Application October 20, 1953, Serial No.387,195

Claims priority, application Netherlands November 4, 1952 2 Claims. (Cl.313-92) The invention relates to a cathode-ray tube having a cone whichis closed by means of a glass window at Iits wide end and contains agenerally at glass plate situated near the window, the inventionVrelating particularly kto the attachment o-f this plate.

llt is often necessary to provide a cathode-ray tube wit-h a glass platewhich is fitted within the cone and on which are provided, for example,a number of electrodes, colour lines, mosaic figures or the like. Such aglass plate was in many cases cemented -to the wall of the cone. Inparticular cases it is necessary for the electrodes secured to theglas-s plate and for color lines or dots; i. e., a fluorescent screen,provided on it to be accurately positioned relatively to the electrodesof the tube. Jn this event it is practically very diicult to providesuch a glass plate properly with-in the cone by cementing it thereto. Afurther difficulty is experienced in that such a glass plate ofcomparatively large size easily cracks when bei-ng in Contact with metalwhich is heated to a high temperature on sealing the window or for otherreasons.

An excellent solution of securing such a glass plate in a cathodearaytube is to hold, in accordance with the invention, the glass plate insuch a cathode-ray tube by means of insulating supporting members which,in turn, are secured to a metal supporting frame. As a matter of fact,the use of insulating members between the metal frame and the glassplate is necessary in order to prevent the temperature from rising toorapidly where the glass plate contacts with the metal frame. In thisevent, the uneven and rapid heating of `fthe metal frame on sealing :theglass to the cone and, as the case may be, on degassing the tube is onlygradually transferred to the glass plate via the insulating memberswhich are poor heat conductors. lf, moreover, the plate is required tobe maintained centred in one or more directions, it is preferably restedin slots of the insulating members so as to center and maintain theglass plate without clearance in the cold state. In event, the metalframe should have a coeicient of expansion higher than that `of theglass plate.

The use of such a metal supporting frame has the additional advantagethat the centering of the glass plate is not adversely effected byTheating. Since the glass plate rests in slots of the insulating membersand 4the metal supporting frame expands more than the glass plate onheating, this plate will come to rest loosely in the slots when sealingthe window or degassing the tube, because the spacing between theinsulating supports increases more than the size of the glass plate.After cooling, the insulating supports resume their initial position dueto shrinkage of the metal frame, with the result that the glass plate isagain centered in its initial position. Since this glass plate issupported in slots it cannot'drop .out when released in the case of hightemperature. The

United States Patents- M A2,781,469 Patented Feb. 12, 1957 metal plateitself maybe secured in the cone in a suitable manner. In the case of ametal cone, this may, for example, be effected by sealing metal stayrods to the inner wall of the cone and by securing the stay rods to thesupporting frame, 4for example, by screwing.

In order that the invention may be readily carried into eiect it willnow be described in detail with reference to the accompanying drawing,given by way of example, in which IFig. l shows a cathode-ray tube, and

Figs. 2 and 3 show details of fastening a glass plate according to theinvention.

In the drawing, the reference numeral 1 denotes a cathode-ray tubecomprising, in the case under review, a metal cone 2 and a glass window3 which may, for example, be sealed to the cone 2, if desired by meansof glaze. A glass plate 4, which is flat in the case under review, isintroduced `into the cone prior to sealing the window 3 and accuratelycentred in one or both directions. The plate 4 is secured to a metalframe 5 by means of insulating members 6 and held without clearance inslots 9 of said insulating members 6 in the cold state. The members 6may, for example, be secured to the frame 5 by means of screw bolts 10.In this instance, the frame 5 is secured to the cone by means of stayrods 7 and 8. The frame 5 has a rectangular opening 11 to enable theelectrons to reach the glass plate 4. On sealing the window 3 to thecone 2, the metal frame 5 is generally also heated at the edges and thismuch more rapidly than the glass plate 4. It has turned out that directcontact between lthe glass plate 4 and the frame 5 nearly always resultsin cracking of the plate 4. This is avoided by attaching the glass plate4 with the interposition of the insulating supporting members 6. Thesemembers are preferably provided with slots. On being heated, lthe metalframe 5 will more expand than the glass plate 4, so that the latter willengage the slots 9 loosely but cannot drop out of them. After cooling,the insulators 6 resume their initial position to the effect of bringingthe glass plate 4 back into its initial position relative to the otherelectrodes and maintaining it therein. Since, upon heating, the glassplate is `released the risk of cracking, notably in the case of at glassplates, is greatly diminished. The insulators 6 preferably consist of aceramic material which is easy to machine after sintering, thuspermitting a slot having the desired depth and height to be turned orground in them. If desired, said insulators may be made up of severalparts, for example, two discs between which a distance piece is clamped,this piece corresponding to the thickness of the glass plate.

Although only one embodiment has been described, it will be evident thatthe invention also applies to other constructions liable to cracking dueto the heating of glass plates secured to a metal plate and, as the casemay be, accurately centred. As an alternative, the glass plate may becurved and alternatively be held so as yto be displaceable in a singledirection.

What is claimed is:

l. A cathode-ray tube comprising an envelope including a glass window atone end, a glass plate having a given c-oeiiicient of expansion disposedwithin the envelope near the glass window and supporting anelectronreceiving member, and means for supporting and centering saidglass plate within said envelope, said supporting means comprising ametal supporting frame mounted on said envelope and having a highercoelicient of expansion than that of said glass plate, and a pluralityof slotted insulating support members secured to said metal -frame andholding and surrounding said glass plate, said fi'siq Q Y .Y Y, ,114,--, Y glass plat'e 'being disposed lwithin the slots of saidl i11-Refe'lene'pa Cited in the lc of this paut sulatingmembers'withoutrclearan at ambient tempera: -ture and being free ofcontact with said metal frame. STATES PATENTS 2. A cathode-ray tube asclaimed in Claim 1 lwherein 2,425,980 Bjrd Aug. 19, 1947 the glass plateis at, and the, electron-receiving member 5 2,611,100 Falkner et alSept. 16, 1952 is a uorescent screen. 2,663,821 Law Dec. 22, 1953

